1. Field of Invention
This invention relates to toys, displays, or music boxes that are activated by light and ago are driven by an electric motor powered by solar panels and/or small batteries.
2. Prior Art
It is a very pleasant experience to watch sunlit, colored, and/or rainbow beams of light projected on the walls of a room when sunlight is refracted and reflected by cut crystals. For a greater effect, we have tried to slowly move crystals when they are exposed to sunlight so that the light beams also move throughout the room and the crystals sparkle. The desired motion is a slow oscillation that rotates the crystals between a clockwise and counter-clockwise (or vice versa) motion. We have tried Christmas ornament motors driven by 60 Hz AC power where the power was reduced to low voltage by a transformer or a voltage divider. We have obtained low voltage DC motors that are highly geared down (found in motor driven dolls) and operated them with solar panels or batteries. We have tried various clockworks which use crystal oscillators for timing circuits. We have tried flexible metal motor shafts to transport the rotation from the relatively large motor gear assembly to the crystal. Finally we have tried bi-metalic devices which move when heated by the sun. These ideas have driven the cost above what we think the market will bear, and they are larger than necessary in our judgement.
In order to reduce cost and size of the device, we have come up with the present design which uses none of the above methods. Also we have achieved the more desirable slow, smooth oscillating rotations that are much more interesting than a steady state rotation because the beams of light stop periodically for a clear vision of the beam patterns. In our invention, we are pulse rotating a motor to minimize the size of the motor, power supply and we are using these pulses to excite the natural frequency of a rotational pendulum (a crystal suspended by a thread) such that the crystal rotates in a smooth oscillating manner. The motor, power supply is energized by a small solar panel or a small, light-activated battery.
To drive the motor, we are using a method common to electrical engineers to produce high current pulses from low DC current supplies. An example of this method is found in the automobile where a capacitor is charged by a low current and then discharged at high current through the primary windings of a transformer coil so that sufficient voltage is generated on the secondary winding to create an arc across the gap of a spark plug.
With a variable charging current (especially from the solar panel), a timing circuit used to trigger the discharge of the capacitor such as those found in U.S. Pat. No. 5,760,572 of Takeda and Fujii would, for the most part, discharge the capacitor either too early or too late. When too early, before the capacitor is charged, there is not enough energy to rotate the motor, or when too late, long after the capacitor is charged, the charging time for the next pulse is lost. The chance of a timed discharge to occur exactly at the time the capacitor just charges is very low. By always discharging the capacitor just as the capacitor is charged, as we do, we maximize the efficiency of rotation and hence minimize the size of the solar panel or battery.
It should be noted that we are not trying to move an object from point A to point B or to store energy for use hours later such as found in U.S. Pat. No. 5,760,572 of Takeda and Fujii and U.S. Pat. No. 4,901,295 of Daho Taguezout and Xuan respectively. We are simply maintaining, more or less, the continuous rotation of a crystal. The motion of the crystal, of course, depends on the motor pulse rate (depending on the solar intensity or the age of the battery) and the natural frequency of the rotational pendulum which depends on the thread length and stiffness, and the moment of inertia of the crystal which is suspended by the thread. We are not using geared down motors to turn crystals slowly and continuously such as found in U.S. Pat. No. 5,232,105 of Gregg.